In certain processes for hot consolidating powder metal, the powder metal is sealed in an evacuated metal container under a vacuum (typically about 10 microns). Thereafter, the filled and sealed container is subjected to heat and pressure, as for example, in an autoclave, to hot consolidate the powder metal. Since the container is maintained under a vacuum it is necessary to perfect a reliable seal subsequent to filling to prevent leakage of gas into the container. Should a leak develop in the container prior to, or during, hot consolidation an unacceptable part will be produced due to the porosity which is caused by the gas entering the container. Containers for hot consolidating powder metal are particularly susceptible to leaks when hot consolidation is carried out in an autoclave due to the fact that the container is subjected to gas pressure between 10,000 and 30,000 psi thereby greatly increasing the difference in pressure between the interior and exterior of the container. Consequently, containers for hot consolidation are carefully tested prior to use to insure their integrity.
In order to fill the containers with powder metal, the containers are provided with a metal fill tube, or tubulation, which communicates with the interior of the container. The fill tube is carefully joined and sealed to the container to prevent leaks between the tube and the container. The fill tube is connected to a source of powder metal and also to means for evacuating the container, such as a vacuum pump. After the container has been evacuated, the container is filled with powder metal. A critical stage of this operation is sealing the fill tube subsequent to the evacuation and filling of the container. One method for sealing the fill tube includes a combination of crimping and welding. More specifically, the end of the fill tube is crimped and folded over one or more times and then welded. This procedure is not only difficult and time consuming, but often results in a leaking container due to cracks formed in the fill tube during crimping or holes formed in the fill tube during welding. The instant invention provides a relatively simple and reliable method for sealing the fill tube which is not subject to the drawbacks encountered in the previously described method.